This invention relates to a liquid ejection apparatus such as an ink jet printer, and a method of controlling the same. This invention particularly relates to a liquid ejection apparatus capable of performing a flushing operation for forcibly ejecting liquid droplets from nozzle orifices, and a method for controlling such a liquid ejection apparatus.
A liquid ejection apparatus is equipped with a liquid ejection head, which can eject liquid in the form of droplets. As a representative example of this liquid ejection apparatus, there is an image recording apparatus such as an ink jet printer which ejects ink droplets onto recording paper, etc., as an ejection target to form dots thereon and thereby carry out recording. Also besides such an image recording apparatus, liquid ejection apparatuses are being applied to various manufacturing apparatuses in recent years. For example, with a display manufacturing apparatus for a liquid crystal display, plasma display, organic EL (electroluminescence) display, or FED (field emission display), etc., a liquid ejection apparatus is used to eject various liquid-form materials, such as color materials, electrode materials, etc., onto pixel forming regions, electrode forming regions, etc.
For example, in the above-mentioned ink jet printer (referred to hereinafter simply as “printer”), this printer is equipped with a the recording head, equipped in turn with pressure chambers, into which ink from an ink cartridge is supplied, a plurality of nozzle arrays formed by nozzle orifices, which are in communication with the pressure chambers, and pressure generating elements, which vary the pressure of the ink in the pressure chambers, and is arranged so that ink droplets are ejected from the nozzle orifices by the driving of the pressure generating elements.
During the recording operation of this printer, the free surfaces (meniscus) of ink at the nozzle orifices of the above-mentioned the recording head are exposed to air. Thus at nozzle orifices, with which the non-ejecting state is sustained during the recording operation, the solvent gradually evaporates and the ink becomes viscous with the elapse of the non-ejecting time, causing the occurrence of such ejection faults, as deviation of the direction of flight of ink droplets, failure of ejection of ink droplets, etc.
When the recording option is not being earned out, the nozzle opened surface of the above-described the recording head is sealed by a cap member to prevent the ink at the nozzle orifices from being viscous. However, in a case where the recording operation is not carried out for a long period of time, the solvent volatilizes and the ink becomes viscous gradually even in this sealed state, causing ejection faults, such as failure of ejection of ink droplets, especially the smallest ink droplets among the ink droplets ejectable by the recording head, to occur at the start of a subsequent recording operation.
In order to prevent such ejection faults in advance, flushing operation for forcibly ejecting ink droplets of a number (prescribed flushing number) necessary for ejecting viscous ink, solidified ink or other unnecessary ink and thereby preventing ejection faults, is carried out independently of the recording operation (eject operation) in this type of printer (see for example, Japanese Patent Publication No. 10-181047A). In this flushing operation, the ejection of a prescribed flushing number of ink droplets from all nozzles is carried out at the position opposing to an ink receiving member. Since the unnecessary ink is ejected by this flushing operation, ejection faults can be prevented in advance.
FIG. 7 is a time chart for describing an example of a flushing operation in a such a printer. With this example, the prescribed flushing number is set to 1000 shots, and first the flushing operation is carried out on odd-number nozzle arrays among the plurality of nozzle arrays until the prescribed flushing number is completed, and thereafter, the flushing operation is carried on even-number nozzle arrays until the prescribed flushing number is completed. Also, prior to the flushing operation of the odd-number nozzle arrays and prior to the flushing operation of the even-number nozzle arrays, a pre-flushing meniscus vibration is carried out. This pre-flushing meniscus vibration is carried out to agitate the ink to some degree to make the unnecessary ink be ejected more readily in the flushing operation.
In recent years, there has been an increasing demand for improvement of the recording operation speed of printers, and the shortening of the time for the flushing operation as much as possible is being desired. However, if the flushing operation is simply shortened, flushing of an amount adequate for preventing ejection faults cannot be carried out.
Also, especially in the case where, after the activation of a printer following a state in which the printer has not been used for a long period of time and a flushing operation is carried out prior to a recording operation, there is a high possibility that viscous ink or solidified ink exists at the vicinity of the nozzle orifices, and since in this case, a large flushing number (number of ejected ink droplets during the flushing operation) is required for ejection of the viscous ink, solidified ink, or other unnecessary ink, much time and a large amount of ink are consumed correspondingly.